1. Technical Field
The present invention relates to a method and system for processing multicast in a unicast-based Voice over Internet Protocol (VoIP) system.
2. Description of the Related Art
In order to provide group message service through the Internet, servers mostly use a method of transmitting the same message data as many times as the number of users. The method places a load on a server and a network in proportion to the number of terminals, but is used in most environments because it is easily implemented and facilitates user management.
On the other hand, a multicast transmission scheme can efficiently use network resources without the above-mentioned repeated transmission of a group message, but it is not easy to apply.
It is best for a conventional VoIP system to use multicast for transmitting the same message data in a group of many users using the Internet.
However, all routers along a traffic path must support a multicast protocol, and transmission trees of respective sessions need to be maintained so that the conventional VoIP system can use multicast.
In addition, commonly used routers do not currently support multicast. Furthermore, the most appropriate method should be selected to construct a transmission tree in total consideration of the number, density and distribution of senders and receivers, which is not an easy task.
In other words, problems of interoperation and disagreement between Internet service providers (ISPs) inhibit the provision of multicast service.
Since it is difficult to provide a service using multicast in a conventional VoIP system, an application-layer multicast scheme has been developed as an alternative method.
The application-layer multicast scheme sets up the transmission order of terminals according to only a unicast transmission scheme of an Internet Protocol (IP) layer, and then transfers data. Thus, the load on the server can be reduced, and traffic can be distributed all over a network in which the terminals are located.
In addition, there is a scheme of converting unicast data into multicast data and relaying it. Likewise, this scheme has an advantage in traffic distribution and can improve the time taken for transferring data to a final terminal.
In the case of the latter scheme, equipment capable of separately processing multicast may be installed in each network, but this requires the installation of additional equipment.
Conventionally invented methods of transmitting a group message are mainly focused on only obtaining multicast effects, and thus do not fully take into consideration matters indispensable for providing a service, such as setup and maintenance of group information. Most methods of transmitting a group message are based on the assumption that multicast transmission scheme is used, and thus are somewhat inappropriate for providing actual service.
In addition, the conventionally invented methods are designed by considering a general data network, rather than a specialized environment such as VoIP, and thus are not easy to apply.